Guide blade fixture in a flow channel of an aircraft gas turbine

ABSTRACT

An arrangement for detachably fixing a guide blade segment that forms part of a transition channel of an aircraft gas turbine comprises high-pressure and low-pressure turbines. The arrangement has a groove-hook-type connection in the front area of the outer platform of the guide blade segment for its radial fixation and at least one pin that penetrates the hook-groove-type connection for securing it against rotation of the guide blade segment.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to an arrangement for fixing a guide bladesegment that forms part of a transition channel.

Modern aircraft gas turbines frequently comprise a so-called core enginewith a high-pressure turbine having a relatively small diameter, whichis arranged downstream from a low-pressure turbine having a relativelylarge diameter. This creates the necessity of transitioning the ringchannel, which extends through the gas turbine and is equipped withguide blades, behind the high-pressure turbine from its small diameterto the large diameter of the low-pressure turbine, which occurs with theaid of a so-called transition channel.

Such engines furthermore have high bypass ratios and low speeds of thelow-pressure turbine shaft, which is generally separated in relation tothe high-pressure turbine shaft; moreover the urgency exists to designthe core engines in an increasingly compact and powerful manner, whichleads to increasingly longer axially extending transition channels withgreater differences between the radii of the channel cross-sections thatneed to be taken into consideration.

Such an arrangement, which is called a “transition duct sealing device”,is known from German publication DE 37 00 668 A1. The inner wall (16) ofthe transition duct consists of several segments (18), which are screwedtogether with the inner shrouds (20) of the guide blade clusters (22).Additional, cone-shaped parts (34, 42) with seal elements (40, 70) arescrewed to the segments (18). The screw connection between the rear cone(42) and the segments (18) permits limited relative axial and radialmovements, with the cone (42) comprising slots (46), in which bolts (32)are guided with some play. Hence the guide blade clusters (22) bear thesegments (18) and the cones (34, 42), and no information is provided onthe fastening of the guide blade clusters (22) on the outer turbinehousing.

German publication DE 24 35 071 C1 protects a stator blade for a gasturbine jet engine, i.e. a guide vane. The guide vane (20) is located onthe downstream end of the combustion device (12) upstream from a turbinerotor stage (16) of the high-pressure turbine. Due to the high gastemperatures directly behind the combustion chamber, the guide vane (20)has an air-cooled design. The pressure of the cooling air is also usedto stabilize and align the multi-part blade design during operation.Hence, no integral, inherently stable guide blade segments exist.

British document GB 2 260 789 A relates to an arrangement for fixingguide blade segments. The guide blade segments (10) are fastened to theturbine housing and guided only via their outer platform, i.e. theirouter band (12). For this purpose each band (12) contains on theupstream end a flange (30) that is hook-shaped in its longitudinalsection. The flange is supported on one side radially on a housing part(32). On the downstream end each band (12) is equipped with a supportmember (26), a hook (22) and a land (24). Each support member (26)engages in the circumferential direction into the recess (24) of theadjoining guide blade segment (10). Between the support member (26),recess (24), and hook (22), a small free space remains, in which a stud(28) that is attached to the housing engages in an axial fashion. Thearea assumes a radial fixation as well as a rotational preventionfunction in the circumferential direction. Furthermore, the bands hererest axially on a housing component (18). In the area of the guideelements (22, 24, 26, 28), the design is relatively complex as wellproblematic from a stability point of view.

This is where the invention comes in, the object of which is to createan inexpensive, easy-to-mount and well-sealing arrangement that is atthe same time, weight-saving, for the attachment of a guide bladesegment that forms part of a transition channel.

This object is achieved pursuant to the invention.

The design pursuant to the invention has a series of advantages. Forexample, a simple and safely functioning seal of the guide bladesegments on the inside and outside, and thus to the disk area betweenthe high-pressure and low-pressure turbine, is possible through thestraight surface contact between the bars and bearing surfaces of thehousing and the bearing pedestal. Through the groove-hook-typeconnection in the front area of the outer platform of the guide bladesegment, these are held radially in the turbine housing in a safe andpermanent fashion and are fixed in the circumferential direction bymeans of the pins engaging in the groove-hook-type connection. Thebearing area located on the turbine housing for accommodating the guideblade segment can at the same time serve as a bearing area for a channelsegment of the transition channel engaging likewise on the bearingsurface so that the mounted guide blade segment of the transitionchannel is a locking element for the channel segment arranged upstream.

The arrangement pursuant to the invention of the grooves on thegroove-hook-type connection on the housing and the arrangement of thehooks on the outside platform part of the channel segment enables asimple and accurate production of these parts, leading to significantweight and cost advantages.

The invention is described in the following based on an exemplaryembodiment illustrated in the drawings in a more or less diagrammaticfashion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial section through a two-stage aircraft gas turbine,which is shown only in part, in the area of the transition channelcomprising the guide blades between the high-pressure and low-pressureparts,

FIG. 2 is a section from FIG. 1 relating to the area of the guideblades;

FIG. 3 is a perspective view of the area of the guide blades pursuant toFIG. 2; and

FIG. 4 is a detail in enlarged view.

DETAILED DESCRIPTION OF THE INVENTION

An aircraft gas turbine 10, which is shown only diagrammatically in FIG.1 in the transition area between the high-pressure turbine HD andlow-pressure turbine ND, contains a flow channel 12 designed as a ringchannel, which leads from the small diameter of the high-pressure partHD to the larger diameter of the low-pressure part ND. This transitionoccurs via a transition channel 14, which comprises downstream a channelsegment 14 a and upstream a channel segment 14 b of special designholding a plurality of guide blades 15, said segment being referred toin the following as a guide blade segment 16.

A housing, which overall has been designated with the number 18 and hasa familiar structure, encloses the high and low-pressure parts of theturbine. Here the bearing pedestal 21 close to the seal 20 located inthe channel intermediate space 22 as well as the bearing surfaces 24, 35and 38 are of interest.

The guide blade segment 16 that bears the guide blades 15 comprises anoutwardly—to the inside wall of the housing 18—directed outer platform30 and an inner platform 32 that faces the axis of rotation 29 of theaircraft gas turbine—see especially FIG. 3—, which bear bars 36 and 37extending in the radial direction 34, respectively. These bars areassigned bearing surfaces 38 or 35 on the housing 18 or on the bearingpedestal 21—see FIG. 2—, on which the bars find axial support in theassembled state of the aircraft gas turbine.

The platform 30 moreover comprises downstream hook-shaped projections 40that are bent against the axial direction 39, of which one projection isequipped with a slot 42, see FIG. 3. These projections 40 are assignedcorresponding grooves 44, which are located in the bearing surfaces 24of the housing 18; see also FIG. 4. One of these grooves is equippedwith an opening 45 that is assigned to the slot 42 for the purpose ofaccommodating a pin 46, as can also be clearly seen in FIG. 4.

By interacting with the hook-shaped projections 40, the grooves 44 forma so-called hook-groove-type connection, which enables a positiveattachment of the guide blade segment 16 in the turbine housing, whereinby means of the pin 46 this segment is also secured against rotationaround the axis of rotation 29.

The design of the bars 36 and 37 of the outer and inner platforms 30 and32 as well as the assigned bearing surfaces on the bearing areas 24affixed to the housing and the bearing pedestal 21 is such that astraight surface contact exists between these surfaces, which enables anoperationally safe seal on the contact areas and hence the disk area ofthe low-pressure turbine.

After installation of the guide blade segment, it forms a lock for thechannel segment 14 a arranged upstream, which is received on the bearingsurfaces 24 of the housing 18 via a strut molding 50.

The above-described arrangement with the hook-groove-type connectionenables a weight- and cost-saving as well as easy-to-handle detachablepositive and non-positive insertion of the transition channel thatcomprises the guide blades into the disk space between the high andlow-pressure parts of the aircraft gas turbine, which is preferablydesigned as a two-shaft turbine. The straight-line contact between thebars of the guide blade segment and the assigned bearing surfacesenables moreover a simple sealing of said segment.

1. An arrangement for fixing a guide blade segment that forms part of atransition channel between the housing and the bearing pedestal of aturbine housing of a high-pressure turbine and a low-pressure turbinewith aircraft gas turbines having different diameters, the transitionchannel transitioning from a smaller diameter of the high-pressureturbine to a larger diameter of the lower pressure turbine, wherein theguide blade segment comprises an outer platform and an inner platformtensioning the guide blades, wherein the outer and inner platforms, foraxial positioning and sealing of the guide blade segment, comprise bars,wherein each of the bars enables a straight surface contact with bearingsurfaces of the bearing pedestal and the turbine housing, wherein theguide blade segment, by way of an upstream groove-hook-type connectionassigned to the outer platform, is held radially on the turbine housingand secured against rotation by way of a substantially radiallyextending pin that engages in a slot defined in a hook of thehook-groove-type connection, and wherein a groove of thegroove-hook-type connection is assigned to one of the bearing surfacesof the turbine housing and the hook of the groove-hook-type connectionis assigned to the outer platform of the guide blade segment.
 2. Anarrangement for fixing a guide blade segment that forms part of atransition channel between the housing and the bearing pedestal of aturbine housing of a high-pressure turbine and a low-pressure turbinewith aircraft gas turbines having different diameters, the transitionchannel transitioning from a smaller diameter of the high-pressureturbine to a larger diameter of the lower pressure turbine, wherein theguide blade segment comprises an outer platform and an inner platformtensioning the guide blades, wherein the outer and inner platforms, foraxial positioning and sealing of the guide blade segment, comprise bars,wherein each of the bars enables a straight surface contact with bearingsurfaces of the bearing pedestal and the turbine housing, wherein theguide blade segment, by way of an upstream groove-hook-type connectionassigned to the outer platform, is held radially on the turbine housingand secured against rotation by way of a pin that engages in thehook-groove-type connection, wherein grooves of the groove-hook-typeconnection are assigned to the bearing surfaces of the turbine housingand hooks of the groove-hook-type connection are assigned to the outerplatform of the guide blade segment, and wherein the bearing surfaces ofthe turbine housing to which the grooves of the hook-groove-typeconnection are assigned also form bearing surfaces for an upstreamchannel segment of the transition channel, which is locked in itsinstalled position by the guide blade segment.
 3. A process of fixing aguide blade segment that forms part of a transition channel between thehousing and the bearing pedestal of a turbine housing of a high-pressureand a low-pressure turbine with aircraft gas turbines having differentdiameters, the transition channel transitioning from a smaller diameterof the high-pressure turbine to a larger diameter of the lower pressureturbine, the guide blade segment comprising an outer platform and aninner platform tensioning the guide blades, the platforms, for axialpositioning and sealing of the guide blade segment, comprising bars,each of the bars enabling a straight surface contact with bearingsurfaces of the bearing pedestal and the turbine housing, the guideblade segment, by way of an upstream groove-hook-type connectionassigned to the outer platform, being held radially on the turbinehousing, a groove of the groove-hook-type connection being assigned toone of the bearing surfaces of the turbine housing and a hook of thegroove-hook-type connection being assigned to the outer platform of theguide blade segment, comprising securing the guide blade segment againstrotation by way of a substantially radially extending pin that engagesin a slot defined in the hook of the hooking-groove-type connection. 4.A process of fixing a guide blade segment that forms part of atransition channel between the housing and the bearing pedestal of aturbine housing of a high-pressure and a low-pressure turbine withaircraft gas turbines having different diameters, the transition channeltransitioning from a smaller diameter of the high-pressure turbine to alarger diameter of the lower pressure turbine, the guide blade segmentcomprising an outer platform and an inner platform tensioning the guideblades, the platforms, for axial positioning and sealing of the guideblade segment, comprising bars, each of the bars enabling a straightsurface contact with bearing surfaces of the bearing pedestal and theturbine housing, the guide blade segment, by way of an upstreamgroove-hook-type connection assigned to the outer platform, being heldradially on the turbine housing, the grooves of the groove-hook-typeconnection being assigned to the bearing surfaces of the turbine housingand hooks of the groove-hook-type connection being assigned to the outerplatform of the guide blade segment, comprising securing the guide bladesegment against rotation by way of a pin that engages in thehooking-groove-type connection, wherein the bearing surfaces of theturbine housing to which the grooves of the hook-groove-type connectionare assigned also form bearing surfaces for an upstream channel segmentof the transition channel, which is locked in its installed position bythe guide blade segment.